Unfortunately this is likely due to the limits in the resolution of V3V4 sequencing, where taxonomic annotation is often limited to the genus rather than species level. There are a few techniques that you could try to improve your results a bit though! The simplest is to simply use the classify-sklearn tool in feature classifier, which generally can give slightly better results. This video rom our Youtube channel discusses the different methods in a bit more detail.
The other thing that you can do is use a weighted taxonomic classifier which has been shown to increase accuracy of taxonomic annotation. Here is the paper and a tutorial for the plugin(q2-clawback).